School of Physics · Southeast University 中文

Research

Research

We explore the fundamental physical properties of novel low-dimensional materials using spectroscopic techniques such as Raman, photoluminescence and ultrafast spectroscopy, modulate their optoelectronic properties through defect, strain and interface engineering, and develop high-performance photodetectors, light-emitting and photovoltaic devices.

01

Spectroscopy of Low-Dimensional Materials

Optical spectroscopies are powerful techniques for studying low-dimensional materials. They are efficient and nondestructive, and the spatial resolution can be varied from the submicrometer to centimeter range by manipulating the focused laser beam. We developed an optical contrast spectroscopy technique to precisely identify the thickness of 2D materials (up to 10 layers), adopt Raman and photoluminescence spectroscopy to investigate defects, doping and electronic band structures, and employ ultrafast spectroscopies including time-resolved PL and optical pump–optical/THz probe to investigate carrier dynamics.

Key References

  1. Ni ZH et al. Graphene thickness determination using reflection and contrast spectroscopy. Nano Letters 7, 2758 (2007)
  2. Ni ZH et al. On resonant scatterers as a factor limiting carrier mobility in graphene. Nano Letters 10, 3868 (2010)
  3. Liu HW et al. Composition-dependent electron transport in CdSxSe1-x nanobelts, a THz spectroscopy study. Optics Letters 39, 567 (2014)
  4. Wu ZT et al. Defects as a factor limiting carrier mobility in WSe2, a spectroscopic investigation. Nano Research 9, 3622 (2016)
02

Modulating the Optical Properties of 2D Materials

There is a great need for controlling the properties of 2D materials to fulfill the requirements of various applications. In optoelectronics, materials are expected to have a finite bandgap, high mobility and strong optical absorption. We focus on modulating the optical properties of graphene and other 2D materials through the control of interlayer interactions, edge chirality, strain and defect engineering.

Key References

  1. Ni ZH et al. Tunable stress and controlled thickness modification in graphene by annealing. ACS Nano 2, 1033 (2008)
  2. Liu YL et al. Layer-by-layer thinning of MoS2 by plasma. ACS Nano 7, 4202 (2013)
  3. Nan HY et al. Strong photoluminescence enhancement of MoS2 through defect engineering and oxygen bonding. ACS Nano 8, 5738 (2014)
  4. Lu JP et al. Bandgap engineering of phosphorene by laser oxidation toward functional 2D materials. ACS Nano 9, 10411 (2015)
03

Laser Micro/Nano Manufacturing

Precise handling of materials is a challenging issue restricting the practical applications of low-dimensional nanomaterials. With high spatial resolution, high energy density and flexibility, laser micro/nano manufacturing is a versatile tool for manipulation, structural transformation, micropatterning and chemical modification. We have devised and optimized laser techniques for patterning, thinning, modification and surface decoration.

Key References

  1. Lu JP et al. Improved photoelectrical properties of MoS2 films after laser micromachining. ACS Nano 8, 6334 (2014)
  2. Lu JP et al. Atomic healing of defects in transition metal dichalcogenides. Nano Letters 15, 3524 (2015)
  3. Lu JP et al. Microlandscaping of Au nanoparticles on few-layer MoS2 films for chemical sensing. Small 11, 1792 (2015)
  4. Lu JP et al. Enhanced photoresponse from phosphorene–phosphorene-suboxide junction fashioned by focused laser micromachining. Advanced Materials 28, 4090 (2016)
04

Optoelectronic Properties and Devices

One of the most promising applications of 2D materials is optoelectronic devices, including photodetection, light-emitting and photovoltaic devices. Together with our collaborators, we have developed a series of 2D material based devices, e.g. graphene mode-locking lasers and optical polarizers, high-performance photodetectors and position-sensitive detectors.

Key References

  1. Wang WH et al. High performance position-sensitive-detector based on graphene–silicon heterojunction. Optica 5, 27 (2018)
  2. Guo XT et al. High-performance graphene photodetector using interfacial gating. Optica 3, 1066 (2016)
  3. Lu JP et al. Hybrid bilayer WSe2–CH3NH3PbI3 organolead halide perovskite as a high-performance photodetector. Angew. Chem. Int. Ed. 55, 11945 (2016)
  4. Wang WH et al. Interfacial amplification for graphene based position sensitive detectors. Light Sci. Appl. 6, e17113 (2017)